[ios/tooling] the install-xcode-template fails if file permissions aren't exactly as expected

It looks like the bash script has no error handling, so when mkdir fails the script isn't able to copy over the templates. Due to the lack of error handling the script still thinks it succeeded

👋 ./ios/tooling/install-xcode-template.sh                                                               (🙈) ~/Developer/ribs💻 
==> Copying up RIBs Xcode file templates...
mkdir: /Applications/xcode_10_fb.app/Templates/File Templates/RIBs: Permission denied
usage: cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file target_file
       cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file ... target_directory
usage: cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file target_file
       cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file ... target_directory
usage: cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file target_file
       cp [-R [-H | -L | -P]] [-fi | -n] [-apvXc] source_file ... target_directory
==> ... success!
==> RIBs have been set up. In Xcode, select 'New File...' to use RIBs templates.

Start with ios/tooling/install-xcode-template.sh and reproduce the failure when creating the Xcode template directory lacks permission. Trace how mkdir and cp failures affect the script's final status. Done means a failed setup is reported as unsuccessful instead of printing success after the copy steps fail.